BART Board of Directors President Bob Franklin (left) and spokesman Linton Johnson try potential new BART train seats during a media preview of the mobile seating lab at Joseph Bort Metrocenter in Oakland on Sunday, April 24.

Photo: Thomas Levinson, The Chronicle

BART Board of Directors President Bob Franklin (left) and spokesman...

If you've ever wished you had a little more leg room on BART, or bemoaned the lack of standing room on your morning commute, speak now.

The transit agency is beginning a monthslong survey of riders today to gauge what they want in a BART seat. Participants can tour a "seat lab" and try out different options, including seats of varying widths and heights.

Afterward, riders will be asked to fill out a written survey that asks about seating preferences as well as more general train issues, such as how best to accommodate bikes and luggage, and how BART should convey information to passengers.

BART, which has the oldest trains of any public transit agency in the nation, is undertaking a 13-year, $3.4 billion project to replace its entire fleet. It has already chosen the actual trains, which will resemble the current fleet but use 5 percent less energy and offer riders three, rather than two, doors on the sides of each car. The extra door is expected to reduce the time passengers take getting on and off.

The inside of the cars, though, is a work in progress, and BART spokesman Linton Johnson said the agency wants to hear from its diverse pool of riders in the coming months.

The survey begins this week with several groups of senior and disabled passengers, who will tour the "seat lab" at the Metropolitan Transportation Commission headquarters in Oakland. In coming months, officials will take the lab on the road to each of BART's nine districts. The times and places of those public meetings have not yet been scheduled.

"Our current fleet cannot carry the crowds of tomorrow," Johnson said. "The current seats were designed to lure people out of their cars in the 1960s. ... Now, we're looking at everything - we want to balance comfort and cleanliness."

Though the seat labs will focus on seat placement, height and width, BART will also ask passengers to weigh in on an oft-debated topic - what the new seats should be made of. BART officials say most customers want to the agency to replace its carpets and upholstered seats while using easier-to-clean materials. However, Johnson said, the agency is bound by strict toxicity, smoke and fire standards that were put in place after a 1979 electrical fire in the Transbay Tube.

"The materials we can use are incredibly limited," he said.

So BART is simply asking passengers whether seat comfort is more important than cleanliness, and for any other comments on seat materials.

Participants also can check out four seat widths, four seat heights, and four options for space between rows of seats. BART now has the widest seats of any train system, at 22 inches; Los Angeles, by contrast, offers 17-inch seats on its metro system.

Riders will probably express very different feelings depending on how they use the system, Johnson said.

Dean Kelly, who rode from Lake Merritt to downtown San Francisco on Sunday with his wife and two children, said the extra door would be nice. But his priority is that air conditioners work on BART trains in the summer.

"When we do ride now, I usually think there's enough space," said Kelly, who was pushing his 4-year-old daughter in a stroller. "I know the seats are kind of dirty, so it would be nice if they were cleaner, I guess, but the size is fine."

BART's interior decorating

If you want to attend one of BART's seat labs, visit bart.gov/cars. The transit agency plans to update the website with the times and places of those meetings, which have yet to be scheduled. You can also sign up for e-mail alerts at that site.